Gaseous reservoir



Dec. 7, 1965 N. REINHARDT GASEOUS RESERVOIR 2 Sheets-Sheet 1 Filed Feb. 25, 1963 FIG. I8

FIG. IC

FIG. 2B

m m m NICHOLAS REINHARDT INVENTOR.

FIG. 3

ATTORNEYS Dec. 7, 1965 N. REINHARDT 3,222,561

GASEOUS RESERVOIR Filed Feb. 25, 1963 2 Sheets-Sheet 2 FIG. 2A

FIG. 2C

NICHOLAS REINHARDT INVENTOR.

ua lvi ATTORNEYS United States Patent 3,222,561. GASEOUS RESERVOIR Nicholas Reinhardt, Lexington, Mass, assignor to Edgerton, Gerrneshauseu & Grier, Inc., Boston, Mass., a corporation of Massachusetts Filed Feb. 25, 1963, Ser. No. 260,654 2 Claims. (Cl. 313-180) The present invention relates to gaseous-discharge devices and the like, and more particularly to reservoirs for replenishing the gas in such devices.

When gaseous-discharge devices such as, for example, rectifiers and thyratrons, are operated, appreciable pressure fluctuations occur during the initial instance of operation. Pressure variations also occur during subsequent life-time operation of such devices. The processes involved in such Variations, including variation caused by so-called clean-up phenomena, are imperfectly understood at present so that resort has been had to the use of pressure-equalizing reservoirs of gas within the gaseousdischarge device. Ideally, by supplying additional gas to the device to replace clean-up losses, the reservoirs should maintain a constant pressure in the tube. Heretofore, gaseous reservoirs have fallen far short of this ideal for a number of reasons. Each has been subject to one or more of the following disadvantages: inefiicient use of power; complicated and expensive components; fragile construction; and poor gas regulation.

Many of the prior art reservoirs are inefficient because power is wasted in producing heat which is allowed to escape from the reservoir area without efficiently generating gas to replace the gas which is lost during tube operation. Prior art devices are characterized by complicated structures having a large number of expensive parts requiring extensive time and labor to assemble. Such reservoirs have the additional disadvantage of a high rejection rate due to their complicated nature and the difiiculty of insuring good reservoir action. Due in part to the complicated structure of prior art gaseous reservoirs, they have been readily susceptible to damage by external shock and vibration which injured the reservoir or important component parts thereby rendering it unuseable and shortening the life of the device. The fourth and perhaps most important disadvantage of the prior art gas reservoirs is the fact that they emit gas in such a way that the tube pressure varies considerably. The reasons for such poor gas regulation is that the reservoirs are atfected by a number of parameters, each of which has an effect upon the amount of gas emitted by the reservoir.

Prior art gas reservoirs have, in general, relied upon metal conduction as their principal means of operation. For this reason, many types of heat shields were employed to cut down the heat looses from radiation so that maximum use of the heat generated by the reservoir heater was attained by confining this heat to the reservoir area and allowing it to pass from the reservoir to the tube by conduction through metal members. Analysis of prior art reservoirs has shown that some of the better units emitted about 65% of their heat by metal conduction and about 30% by radiation. The remaining 5% of the reservoir heat was transferred by gas conduction. The chief disadvantage of heat transmission from the reservoir by metal conduction is that there is a linear relationship between the power dissipated by the reservoir and the reservoir temperature. This linear function requires that the power used by the reservoir heater be cont-rolled within very close limits in order to maintain the reservoir temperature within prescribed limits to prevent burn-out of the reservoir. Furthermore, the ambient temperature of the device had a direct effect upon the reservoir and its operating temperature. With a constant power dissipation from the reservoir, increases in ambient temperature would correspondingly cause proportionate increases in reservoir temperature which could be injurious to the reservoir itself or upset the pressure equilibrium in the device.

An object of the present invention, accordingly, is to provide a new and improved gas reservoir of the above described character that shall not be subject to these disadvantages, but that shall, to the contrary, provide for release of occluded or absorbed gas without substantial change in pressure for the required temperatures and pressures dictated by the gaseous-discharge device in which the reservoir is house-d. In summary, this end is achieved by a novel reservoir configuration in which heat is emitted principally by radiation while metal conduction is reduced to a minimum. A heater element, sandwiched between a pair of thin plates containing predetermined amounts of an occluded or absorbed gas, heats the plates uniformly to emit gas in response to changes of pressure in the device.

A further object is to provide a new and improved gaseous-discharge device employing such a novel reservoir.

Still another object is to provide a novel gas supply apparatus of more general utility as well.

Other and further objects will be explained hereinafter and will be more particularly pointed in the appended claims.

The invention will now be described in connection with the accompanying drawings, of which:

FIGURES 1A and 1B are isometric views of the side and top of a preferred reservoir construction, respectively.

FIGURES 2A, 2B, 2C, and 2D are examples of various heater configurations.

FIGURE 3 is a longitudinal section of a preferred reservoir construction in a gaseous discharge device.

Referring now to FIGURES 1A and 1B, the gas reservoir is shown having a pair of similar thin, metal plates 15 and 25, preferably of titanium, with a heater 30 disposed therebetween. Thin plates are preferred for uniform heating and more efiicient gas emission. Two or more such plates may be used on each side of heater 30 in which case they are bonded together prevent spacing therebetween which would impede uniform heating. Plates 15 and 25 are gas loaded to a predetermined level to enable them to emit gas in response to pressure changes within the device housing the reservoir.

Heater 30 is a thin fiat metallic conductor of, for ex ample, molybdenum or the like. The heater 30 may be formed in any of a number of configurations such as those shown in FIGURES 2A, 2B, 2C or 2D or any like arrangement as long as the adjacent portions are disposed close together so that the heater element fills the maximum area with a minimum interspace between adjacent heater portions. The heaters of FIGURES 2A and 2B have a circular perimeter, the former following a spiral path and the latter a zigzag path. In FIGURE 2C the heater has a square perimeter while in FIGURE 2D the perimeter is rectangular. The perimeter of the heater depends upon the shape of plates 15 and 25. Both the plates 15 and 25 and the heater element 30 are preferably of the same overall shape and substantially coextensive in order to efficiently heat the plates to a uniform temperature.

It is important for uniform heating that the heater 30 be of substantially uniform thickness and width throughout because, as is well known, the electrical resistance of the heater is a function of the thickness of the metal conductor, as well as its width. Molybdenum and many other metals have, in the past, been diflicult to form into thin broad heater elements by well-known meta-l processing methods. A preferred method for so forming this heater element is fully disclosed in my application for Letters Patent, Serial Number 273,819, filed April 18, 1963.

To provide the necessary insulation and to enable the adjacent heater elements to be disposed a minimum distance from each other, thin alumina coating may be appiled by sintering and firing at an elevated temperature, or it may be applied at room temperature by spraying the atomized molten insulating material directly on to the heater element as disclosed in United States Letters Patent No. 2,919,373, issued on December 29, 1959, to Daniel F. Riley et al. Other well-known insulating materials may also be used. It should be noted that the adjacent portions of the heater element 30 may be placed so close together that when the insulating coating 40 is applied, the coating on one portion may be in actual contact with the coating on an adjacent portion. The portions must, of course, be insulated from each other to preserve the uniform flow of current through all portions of the heater element thus producing uniform heating of the plates and 25.

Plates 15 and are placed in contact with the insulative coating of heater 30 to insure maximum heat transfer from the heater 30 to the gas-loaded plates 15 and 25 and to provide substantially uniform heating of the plates. By heating the plates to uniform temperatures, a serious disadvantage found in many prior art reservoirs is eliminated. This disadvantage may be referred to as a circuit effect. When different temperatures are pres ent in the gas-loaded metal, the hotter sections may emit gas and, at the same time, the cooler sections may be absorbing gas thereby, in effect, be producing a gas circuit. In the present invention, the plates are uniformly heated to maintain the temperature substantially cont-ant throughout and the circuit effect is prevented.

The plates 15 and 25 and heater 30 are rigidly mounted in position by a plurality of short pins 12, preferably three, disposed substantially equidistant about the reservoir and attached by any of the well-known methods, for example, welding to the walls of the cathode 5 (see FIGURE 3), or to any grounded current return path. A material of as low a heat conductivity as possible consistent with mechanical strength is used for pins 12. Examples of such materials are Hastelloy B and Kovar. By connecting pins 12 to a grounded current return path, only one lead, insulated conductor 13, need be passed through the envelope wall to a source of heater power (not shown). One end of heater 30 is connected to insulated conductor 13 and the other end of the heater is connected to the grounded current return path through pins 12. A separate return conductor may also be used, if desired.

Warm-up time of the reservoir is reduced because the design of the heater 30 provides uniform current flow through all parts thereby eliminating the presence of hot and cold spots which delay temperature equilibrium.

This reservoir, unlike those of the prior art, operates on heat transfer from plates 15 and 25 principally by radiation. In so doing, heat shields which were an important part of old reservoirs, are eliminated. By utilizing the radiation principle, the advantages of the Stefan Boltzmann law are applied to reservoir heat dissipation. This law is expressed as w=pa'(T T or w=p1T Where:

w=power in watts =emissivity of the plates 15 and 25 a=Stefan Boltzmann constant T=temperature of plates 15 and 25 T =ambient temperature Since heat transfer by radiation follows the Stefan Boltzmann law, there is no longer a linear relationship between the power given off by the reservoir and its temperature, but rather, a fourth power relationship now exists. This is important because, at reservoir operating temperatures, changes in the power applied to the reservoir heater 30 from the heater power supply produce very little change in the reservoir temperature. For this reason, a much wider range of heater voltage may be used that was previously possible. I have found this reservoir may be used with heater voltages that vary by plus or minus 15% to 20% or more. Another advantage is that reservoir temperature is affected to only a relatively small degree by changes in the ambient temperature on the walls of the device in which the reservoir is housed.

The reservoir 4 of the present invention is shown in FIGURE 3 in a ceramic vessel thyratron-type such as described in US. Letters Patent No. 3,075,114, issued on January 22, 1963, to Kenneth J. Germeshausen. Therein is shown a cup-shaped anode electrode 1, an inverted cup-shaped control electrode 3, and a vane-type cathode electrode 5 such as that disclosed in US. Letters Patent No. 2,937,302, issued May 17, 1960, to Seymour Goldberg. These three electrodes are provided with flanges 1, 3' and 5 respectively sealed between ceramic vessel wall sections 2, as explained in US. Letters Patent No. 2,842,699, issued on July 8, 1958, to Kenneth J. Germeshausen et al. The control electrode 3 may be apertured as at 7 and disposed close to the anode 1, and a grid baffle 9 overlying the apertures '7 may also be provided. A cathode baffle 11 may also be employed. Another cathode bafiie 14 may be disposed intermediate the heated cathode 5 and reservoir 4. A fuller description of the tube and further details of its construction are omitted in order not to retract from the novel features of the present invention.

In actual operation, gas, for example, hydrogen, is given off by the reservoir in response to changes in the pressure and temperature of the discharge device. As gas is used up in the device by the aforementioned cleanup process, the reservoir supplies additional gas to the device. It is, of course, impossible to regulate the gas emitted by the reservoir to maintain the gas at an exact predetermined pressure, but, by operating on temperature and pressure differences between the device and the reservoir, the gas pressure Within the device may be kept within a safe operating range. As gas is emitted by the reservoir, it constantly requires an infinitesimal increase in temperature to emit more gas when it is needed. Because of this, the increased operating power range of this reservoir extends the life of the device.

The simple structure of the invention is apparent from the drawings and the foregoing description. This simple structure secured in position provides a rugged reservoir capable of withstanding shock and vibration from external sources.

As an example, the reservoir shown in FIGURES 1A and 1B was made up of a pair of circular titanium plates approximately 1 inch in diameter and 0.01 inch thick, and a molybdenum heater 0.005 inch thick Without insulation and 0.018 inch with insulation applied. The heater voltage range was 5.4 to 7.6 volts with a warm up time of about 4 minutes at 5.8 volts and about half that time at 7.6 volts. At 6.3 volts, the heater operating temperature was about 800 C. and in a life test, the reservoir operated for over 2,400 hours with no indication that the maximum life has been reached. In this reservoir, heat transfer was about 66% by radiaiton, 33% by gas conduction and only about 1% by metal conduction.

Other modifications or changes in our invention will be apparent to those skilled in the art and all such are deemed to fall within the spirit and scope of my invention as hereinafter claimed.

I claim:

1. A gaseous-discharge device comprising:

a closed vessel containing a plurality of electrodes and a gaseous medium of predetermined pressure;

a gas reservoir within the vessel comprising a pair of thin plates disposed substantially parallel to each other, each plate containing an absorbed gas, a heater disposed between and in surface-to-surface contact with said plates, substantially coextensive therewith, said heater having a wide, thin heating element disposed with its broad dimension substantially equidistant from said plates and having a minimum spacing between adjacent portions, said heater element being covered with a thin insulating material;

means for connecting the heater to a source of potential; and

mounting means for securely positioning the reservoir Within the vessel, said mounting means having a low heat conductivity constant.

2. A gaseous-discharge device comprising:

a closed vessel containing a plurality of electrodes and a hydrogen medium of predetermined pressure;

a hydrogen reservoir within the vessel comprising a pair of thin, planar titanium plates disposed substantially parallel to each other, each plate containing absorbed hydrogen, a molybdenum heater disposed between and in surface-to-surface contact with said plates, substantially coextensive therewith, said heater having a wide, thin heating element disposed with its broad dimension substantially equidistant from said plates and having a minimum spacing between adjacent portions, said heater element being covered with a thin insulating material;

means for connecting the heater to a source of potential;

and

mounting means for securely positioning the reservoir within the vessel, said mounting means having a loW heat conductivity constant.

References Cited by the Examiner UNITED STATES PATENTS 2,504,335 4/1950 Jonker 3 l3340 2,919,373 12/1959 Riley et al 313--340 2,941,109 6/1960 Senior et a1 3l3340 FOREIGN PATENTS 844,155 8/1960 Great Britain.

GEORGE N. WESTBY, Primary Examiner.

25 ROBERT SEGAL, Examiner.

R. JUDD, Assistant Examiner. 

1. A GASEOUS-DISCHARGE DEVICE COMPRISING: A CLOSED VESSEL CONTAINING A PLURALITY OF ELECTRODES AND A GASEOUS MEDIUM OF PREDETERMINED PRESSURE; A GAS RESERVOIR WITHIN THE VESSEL COMPRISING A PAIR OF THIN PLATES DISPOSED SUBSTANTIALLY PARALLEL TO EACH OTHER, EACH PLATE CONTAINING AN ABSORBED GAS, A HEATER DISPOSED BETWEEN AND IN SURFACE-TO-SURFACE CONTACT WITH SAID PLATES, SUBSTANTIALLY COEXTENSIVE THEREWITH, SAID HEATER HAVING A WIDE, THIN HEATING ELEMENT DISPOSED WITH ITS BROAD DIMENSION SUBSTANTIALLY EQUIDISTANT FROM SAID PLATES AND HAVING A MINIMUM SPACING BETWEEN ADJACENT PORTIONS, SAID HEATER ELEMENT BEING COVERED WITH A THIN INSULATING MATERIAL; MEANS FOR CONNECTING THE HEATER TO A SOURCE OF POTENTIAL; AND MOUNTING MEANS FOR SECURELY POSITIONING THE RESERVOIR WITHIN THE VESSEL, SAID MOUNTING MEANS HAVING A LOW HEAT CONDUCTIVITY CONSTANT. 